The present invention relates to a digital camera and a control method thereof and more specifically, to a digital camera using a shutter curtain which operates mechanically and using an area image sensor which does not have a structure for a high-speed draft mode, and a control method thereof.
A CCD area image sensor which divides electric charges stored in photodiodes into charges of a plurality of divided fields to transfer them is known (refer to, for example, JP-A-8-18875 and Japanese Patent No. 3009041). By dividing electric charges stored in photodiodes into charges of a plurality of divided fields to transfer them, the area of the vertical CCD can be reduced. As a result, since the area of the photodiodes can be increased, this becomes advantageous from the viewpoint of the saturated amount of signals. A digital camera provided with an electronic viewfinder is often mounted with an area image sensor corresponding to a high-speed draft mode, with a function of selectively reading charges at regular intervals from a plurality of photodiodes, which are arrayed along the vertical CCD, in order to increase the frame rate of a moving image which is displayed in real time on the electronic viewfinder. Since the area image sensor corresponding to a high-speed draft mode is provided with a dedicated control signal line for reading the charges stored in the photodiodes at one time by thinning out them according to a rule capable of forming a color image, pixels in a vertical direction from all pixels can be thinned out and read out. As a result, since a grainy image representing a whole image, that is, an image having a low resolution can be read, the frame rate of a moving image can be increased by reading the grainy image in a short time.
However, since a digital camera provided with a high-resolution CCD image sensor which is not corresponding to the high-speed draft mode cannot increase the frame rate of a moving image, it has a difficulty in realizing a moving image display function by the electronic viewfinder. In a digital camera provided with a high-sensitivity and high-resolution CCD image sensor, exposure is often by a shutter curtain which operates mechanically.